摘要:
Provided is a Doppler based automated direction finding system that detects radio frequency (RF) leaks in a cable television plant. During a ride-out, the system detects leaks and stores leak data, such as amplitude, location, and bearing. The stored data is uploaded to a computer that performs a leak analysis. The leak analysis isolates the leaks using Doppler-based bearing information and separates cable leaks from other RF sources, such as power sources and noise. Erroneous information that results from RF reflections (multi path) may be eliminated while processing the data using triangulation. After the leak analysis, the computer generates work orders and maps, makes the data available to users, and may also compile information and file reports based on the data.
摘要:
A method for acquiring azimuth information enables acquisition of azimuth information by receiving signals transmitted by GPS satellites using only a single antenna. The method includes steps of disposing a GPS planar antenna having a hemispherical beam with its beam center horizontal to form a sky coverage area of antenna sensitivity that is a sky quarter-sphere in the direction the GPS antenna faces, causing a GPS receiver connected to the GPS antenna to attempt reception of signals transmitted by GPS satellites, inputting the received signals to a data processing unit to discriminate satellites present in the coverage area, arranging the satellites found to be present in the sky coverage area in clockwise order as viewed from the start azimuth of the sky coverage area; extracting the azimuth of the satellite corresponding to the last term in the order as a start azimuth and the direction opposite the azimuth of the satellite corresponding to the first term in the order as an end azimuth, using the extracted start azimuth and end azimuth to limit the azimuth of the direction in which the antenna faces, and outputting the limited azimuth information as voice message or an image using a result output unit.
摘要:
A method and computer program product are disclosed for locating signal jammers in a digital beamforming receiver having an antenna with a plurality of associated antenna orientations. An associated antenna gain value is calculated for a first of a sequence of the plurality of antenna orientations at each of a series of sample points. The antenna gain values from the first antenna orientation are evaluated for null spaces to obtain a set of candidate null locations. Associated antenna gain values are calculated and evaluated for subsequent antenna orientations only at the set of candidate null locations. Candidate null locations are eliminated from the set after any evaluation in which they are not found to be null spaces.
摘要:
A system is provided for assisting in the detection and tracking of narrowband signals arriving at an antenna array operating over a wide detection bandwidth and in a crowded RF environment. Since the nature of the detection mission is constrained to be a general search, the system does not attempt to detect signals of interest via matched filtering mechanisms (i.e. training sets), but exploits general properties such as power, frequency, time and angle of arrival. For the purposes of providing sufficient Frequency/Time resolution as well as to avoid array overloading in the detection process, the digitized wideband streaming data is frequency channelized using a sufficiently high revisit rate for the signal set of interest, constrained by the required feature detection accuracy or environment adaption rates. Within each frequency subchannel, efficient array signal subspace tracking techniques are used to separate and track spatially separated cochannel signals. Subspace tracking allows the efficient update of the signal subspace, useful for direction finding and copy applications, as well as determining the number of signals present in a frequency channel. Since the frequency channelization of the detection system may not match that of the detected signal, the combination of Time/Frequency/Space information is used to cluster or group frequency subchannels and provide a higher degree of signal detection capability with an increased robustness against false signal detections.
摘要:
A digital GPS receiver includes electronics to detect the presence of multipath GPS signals, determine the direction from which they are received at a multi-element GPS phased array antenna, adaptively generate an antenna pattern to provide gain in the direction of the desired GPS satellite signal, and to apply nulls in the direction of the detected GPS multipath signals. This adaptively-generated antenna pattern is applied to the signals received at the elements of the GPS phased array antenna to provide a composite signal to each of the processing channels of the digital GPS receiver, optimized for the particular GPS satellite being tracked by a corresponding channel. The undesirable multipath GPS signals are thereby excised from the inputs to the processing channels of the digital GPS receiver, and the desired direct signal is reinforced, thus enabling tracking loops within the digital GPS receiver to make highly accurate observations of the code and carrier phase using conventional signal processing techniques.
摘要:
An apparatus for providing GPS positioning information to a master computer and a plurality of slave computers from only one GPS receiver. The apparatus includes a circuit adapted to be coupled between the GPS receiver and the computers for providing each computer with a replica of a positioning information signal from the GPS receiver so that each computer receives all of the positioning information it would have received if it had been connected to its own GPS receiver. In addition, the apparatus includes a circuit adapted to be coupled between the GPS receiver and the computers for providing each computer with a replica of a synchronizing signal from the GPS receiver so that each computer receives the synchronizing signal it would have received if it had been connected to its own GPS receiver. Further, the apparatus includes a circuit adapted to be coupled between the GPS receiver and the master computer for passing a control signal from the master computer to the GPS receiver to set up and control the state of the GPS receiver.
摘要:
A GPS receiver utilizes measurements which span previous and current times, such as delta phase measurements, in a modified Kalman filter. The modified Kalman filter updates position information relating to both the current and the previous times, and s propagates the current position and velocity related information. Using both the current and the previous position related information in the filter in conjunction with delta phase measurements, essentially eliminates the effect of system dynamics from the system model, and a position difference can thus be formed that is directly observable by the phase difference measured between the previous and current time epochs.
摘要:
Apparatus provides information to a mobile user. The apparatus includes a mobile communications system having a fixed part and one or more mobile parts for communicating with the fixed part. The fixed part is adapted to receive one or more requests for user-specific information from the mobile part, and to provide the user with information relating to the or each request. Preferably the mobile user has access to permanent user-specific information and/or non-permanent user-specific information, and the mobile part is adapted to send said permanent user-specific information and/or non-permanent user-specific information to the fixed part.
摘要:
A GPS receiver (26) for processing GPS satellite signals and adapted for connection to a client device (24). The receiver (26) includes a down converter (44), a correlator (46), and a microcomputer A. The microcomputer A has a microprocessor A, a first memory (48A), a second memory (48B, 148B), and an input/output interface (50). The input/output interface (50) is capable of being connected to the client device (24). The first memory (48A) contains a first set of instructions for the microprocessor A to download and store in the second memory (48B, 148B) at least one time critical GPS software module (A1, A2, . . . AN) from the client device (24). The first memory (48A) also contains a second set of instructions for the microprocessor A to determine whether to download and store in the second memory (48B, 148B) a plurality of non-time critical software modules (B1, B2, . . . BN) from the client device (24).
摘要:
By using the GPS satellite transmitted signals that are tracked on a satellite and those that should be tracked but are not due to the attitude of the satellite and rotating the satellite, two estimations of satellite attitude are made that are used to change the satellite attitude so that all the GPS signals are tracked.